Differentiating between normal human activity and suspicious behavior is a difficult task, whether performed by a sensing device or a human observer. A human observer would find such a task tedious and costly to perform in money and time. Fortunately, a sensing system is not bothered by ‘tedious’ tasks. Such a system could be implemented to prune out obviously normal behavior, and tag human activities which could be suspicious and would therefore need more attention by a human operator.
However, such “behavior recognition” systems have not been developed due to the difficulty of identifying and classifying such motions. Consider an urban environment as illustrated in FIG. 1. In such an environment, there are many moving objects and people, most of which are not actively engaged in criminal or destructive behavior. All of these activities would have to be viewed and identified before they could be removed from potential further consideration by a human.